Various types of wind socks have been in use at airports around the world to indicate wind direction. Typically, these wind socks are mounted on an upright post and utilize a truncated, conical framework carrying a fabric which catches the wind and causes the framework to rotate about a vertical axis as the wind changes direction. Various wind sock and wind direction indicators are shown in U.S. Pat. Nos. 1,879,267, 2,404,933, 4,204,271, 3,537,310, 1,359,406, 1,942,039, 1,422,922, 1,742,574, and 1,776,111.
Since aircraft landings occur both in daylight and at night, it is essential that a wind sock indicator be well illuminated for nighttime visibility. Prior to the present invention, the illumination of commercially available wind socks has been accomplished by a system of stationary, incandescent bulbs positioned above the wind sock and rigidly carried by the supporting oost. Typically, the light system utilizes four light fixtures with a fixture attached to each of four radially, horizontally extending arms which are at right angles to one another and are connected to the top of the post. The light fixture on each arm has a light bulb which is aimed downward so that when the wind sock rotates into a position below the specific light, that light will illuminate the top of the wind sock. In effect, when the wind sock is in any given position, it is unusual for more than one or two of the lights to be substantially illuminating the wind sock and mostly, it is the upper half of the sock which is illuminated.
While the described lighting configuration provides an acceptable illumination system, the described system is exceptionally vulnerable to early bulb failure because the light fixtures, which are rigidly mounted to the post, undergo excessive vibration due to the constant changes in wind direction and gusting. Such vibration significantly shortens the life of bulb filaments and causes premature failures. Still another shortcoming is that the four bulbs needed for adequate illumination as the wind sock rotates about its axis, consume extensive electrical energy and only two, at most, are typically illuminating the sock. To the extent that fewer bulbs could be used, a significant saving in electricity is possible. Finally, while the four bulbs provide satisfactory illumination of the rotating wind sock, the fact that only one or two of the bulbs is illuminating the sock at any given time can result in uneven illumination of the sock, and it would be desirable to have a brighter, more evenly illuminated sock in order to observe the sock clearly at greater distances. As will be appreciated, should one or more of the bulbs fail, the wind sock may be still less effectively illuminated. For the above reasons, it is desirable to provide an improved wind sock which has more effective illumination, which requires less energy, and which has longer bulb life. The present invention provides an answer to these shortcomings.